Ubuntu uses Notify OSD (based on libnotify) to display notifications on the desktop. However, the notification bubbles fade away within a few seconds and you may miss them if you are not in front of your computer. Recent Notifications is a very useful Gnome panel applet to display Notify OSD notification history.
To install on Ubuntu, run:
$ sudo add-apt-repository ppa:jconti/recent-notifications $ sudo apt-get update $ sudo apt-get install indicator-notifications